
<h2>Fixation</h2>
Nitrogen in its gaseous form (N2) can’t be used by most living things. It has to be converted or ‘fixed’ to a more usable form through a process called fixation. There are three ways nitrogen can be fixed to be useful for living things:
<h3>Biologically: </h3>
Nitrogen gas (N2) diffuses into the soil from the atmosphere, and species of bacteria convert this nitrogen to ammonium ions (NH4+), which can be used by plants. Legumes (such as clover and lupins) are often grown by farmers because they have nodules on their roots that contain nitrogen-fixing bacteria.
<h3>Through lightning: </h3>
Lightning converts atmospheric nitrogen into ammonia and nitrate (NO3) that enter soil with rainfall.

Answer:
I know you only need two, but here:
--Subsidence and sinkholes.
--Sinkholes and caverns.
--Waterfalls and rapids.
--Deltas and levees.
--Erosion and abrasion.
Explanation:
Answer:
a. population
Explanation:
Gene flow cannot occur in hybrids because 99.9% of the time hybrids offspring are not fertile.
At genus level is not possible either because a hybrid is a cross breed at the genus level (horse-donkey).
A population is a group of species of 1 kind. A population of donkeys.
I believe it is gel electrophoresis.
Gel electrophoresis is a techniwue used to separate DNA fragments or other macromolecules such as RNA and proteins based on their size and charge. It can also determine the actual size of a piece of DNA by examining it next to a standard "yardstick" made up of DNA fragments of known sizes.